Hybrid Dual Electric and Hydraulically Operated Phaser

ABSTRACT

A hybrid dual phaser assembly is disclosed for mounting to an engine camshaft to allow the timing of two sets of cam lobes to be phased independently of one another relative to a crankshaft of the engine. The phaser assembly comprises an electrically operated phaser having intermeshing gears for transmitting torque to the camshaft and a phase control input driven by an electric motor to be mounted coaxially with the camshaft, and a hydraulically operated phaser having vanes movable within arcuate cavities. The cavities of the hydraulically operated phaser are defined in part by an annular member that radially surrounds, and axially overlaps, a gear of the electrically operated phaser, which gear is separate from the annular member and forms radially inner boundary walls of the cavities.

FIELD

The present invention relates to a phaser for acting on two groups ofcam lobes of a valve train of an internal combustion engine to changethe phases of each of the two groups of lobes independently of oneanother relative to the phase of the engine crankshaft. Such a system isherein referred to as a dual phaser.

BACKGROUND

The use of phasers is becoming increasingly widespread on both gasolineand diesel engines. In the past, hydraulically operated phasers haveoffered a compact and cost-effective solution. However, more recently,electrically operated phasers have become popular due to the functionaladvantages that they offer. These advantages include (i) faster responsetime, (ii) more consistent response times over all engine operatingconditions, particularly low temperatures when oil viscosity reduces theperformance of hydraulically operated phasers, and (iii) reduced oilconsumption and oil pump power consumption.

An electrically operated phaser generally consists of two maincomponents, namely a gear set or harmonic drive that is mounted to theengine camshaft, and an electric motor which is mounted to a stationarypart of the engine and positioned coaxially with the camshaft. There maybe a drive coupling (such as an Oldham coupling) to allow for any smallmisalignment between the axes of the motor and the camshaft. Phase isadjusted using an electrically operated phaser by varying the speed ofthe electric motor relative to that of the camshaft. If the motor speedis synchronized with camshaft speed, then the prevailing phase settingis maintained. Reducing the motor speed relative to the camshaft willcause the phaser to move in one direction, increasing the motor speedwill cause the phaser to move in the other direction. A typical exampleof an electrically operated phaser is to be found in U.S. Pat. No.8,682,564.

In some variable valve systems, such as that shown in EP 1417399, aphaser is used to adjust the valve lift profile characteristics. In sucha system, operation of the phaser affects engine power output and thefaster response of an electrically operated phaser would offerdrivability advantages.

Many twin camshaft engines are now being designed with multiple phasersand, in some cases, these are of different types, one camshaft utilizinga cost-effective hydraulically operated phaser whilst the other uses anelectrically operated phaser for its additional speed and consistency.For example, some engines utilize an electrically operated phaser tocontrol the intake valve timing and a hydraulically operated phaser tocontrol the exhaust valve timing.

EP 3141711 shows a hybrid dual phaser having an electrically operatedphaser and a hydraulically operated phaser combined into a single unitfor independently controlling the timing of two groups of cam lobesmounted to an adjustable camshaft, which is also referred to herein as aconcentric or as an assembled camshaft. This device could be applied toan engine having a single camshaft to allow independent control ofintake and exhaust valve timing or it could be applied to an engine witha cam summation valvetrain system such that one output of the dualphaser controls valve lift and duration whilst the other output controlsthe lift timing.

The dual phaser of EP 3141711 shows how the hydraulic and electricsections of a hybrid phaser can be arranged and connected axially, but,in some applications, there is limited axial space available making itdifficult to implement such a solution.

OBJECT OF THE INVENTION

The invention therefore seeks to provide a hybrid dual phaser, comprisedof a hydraulically operated phaser in combination with an electricallyoperated phaser, that has a reduced axial length and that offers asignificant package space advantage in some applications.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a hybrid dualphaser assembly for mounting to an engine camshaft to allow the timingof two sets of cam lobes to be phased independently of one anotherrelative to a crankshaft of the engine, wherein the phaser assemblycomprises an electrically operated phaser having intermeshing gears fortransmitting torque to the camshaft and a phase control input driven byan electric motor to be mounted coaxially with the camshaft, and ahydraulically operated phaser having vanes movable within arcuatecavities, wherein the cavities of the hydraulically operated phaser aredefined in part by an annular member that radially surrounds, andaxially overlaps, a gear of the electrically operated phaser, which gearis rotatable relative to the annular member and forms radially innerboundary walls of the cavities.

By “axially overlaps” it is meant that at least one plane normal to theaxis of rotation of the dual phaser assembly passes through both theelectrically operated phaser and the hydraulically operated phaser. Inthis way, a dual phaser assembly of the invention combines anelectrically operated phaser with a hydraulically operated phaser byarranging the arcuate working chambers radially around the electricallyoperated phaser in the same plane normal to the axis of rotation of thephaser. Packaging the electrically operated phaser radially inside thevane phaser minimizes the axial packaging space requirement whilstallowing the available radial space to be fully utilized.

The electrically operated phaser is controlled by the electric motor,which is mounted coaxially with the camshaft and the hydraulicallyoperated phaser may be controlled by oil feeds connected to aproportional control valve via oil drillings in the camshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a drive diagram relating to a first embodiment,

FIG. 2 is an exploded view of the first embodiment of a dual phaser,

FIG. 3 is an exploded view showing the manner in which the dual phase ofFIG. 2 is assembled to a camshaft,

FIG. 4 is a section of the dual phaser of the first embodiment takenthrough the axis of the camshaft in the plane designated IV-IV in FIG.5,

FIG. 5 is a section of the dual phaser of the first embodiment takenthrough the plane designated V-V in FIG. 4,

FIG. 6 is a drive diagram similar to that of FIG. 1 relating to a secondembodiment, and

FIG. 7 is an exploded view of the second embodiment of a dual phaser.

DETAILED DESCRIPTION OF THE DRAWINGS

The drive configuration of a first embodiment of the invention is shownin FIG. 1. Drive from the engine crankshaft is applied to two phasersactuated in parallel, each of the phasers being connected for rotationwith a respective timing wheel and driving a respective set of camlobes. This drive configuration differs from the configuration shown inFIG. 6 that is employed by the second embodiment of the invention. Inthe case of the configuration of FIG. 6, the phaser of the second set ofcam lobes is connected in series, instead of in parallel, with thephaser driving the first set of cam lobes. In this way, the first phaseracts on both sets of cam lobes, while the second alters the relativephase between the first and the second set of cam lobes.

The construction of the phaser of the first embodiment of the inventionis shown in FIGS. 2 to 5. The dual phaser of the first embodimentcomprises an electrically operated phaser and a hydraulically operatedphaser disposed in overlapping axial planes with the hydraulicallyoperated phaser radially surrounding the electrically operated phaser.The drive input to both the hydraulic and electrically operated phaserscomprises a sprocket 111 driven by the engine crankshaft (not shown)that also forms a rear end-plate 110 of the hydraulically operatedphaser. This rear end plate 110 is fixed for rotation with a front-endplate 112 of the hydraulically operated phaser via three vanes 114 andclamping screws 116. The front-end plate 112 also serves as the driveinput to the electrically operated phaser. The front end plate 112 isalso formed with an internal gear 118 that serves as the input gear ofthe electrically operated phaser and drives the output gear 136 via aninternal gearset 120 that is driven by an external motor (designated 180in FIG. 4) to rotate epicyclically relative to the input gear 118 andthe output gear 136.

The drive output of the hydraulically operated phaser is formed as anannular plate 122 partially defining three arcuate cavities 124. Theinner radial surface of each cavity 124 is defined by the outer surfaceof the output member 136 of the electrically operated phaser. Eachcavity 124 contains one of the vanes 114 connecting the front and rearplates 110,112. The three vanes 114 form a seal between the surface ofthe output gear 136 and the surface of the annular plate 122. The rearend plate 110 of the dual phaser is provided with three large slots 126to allow access for a drive connection from the hydraulically operatedphaser output plate 122 to the camshaft 160.

Timing feedback from the hydraulically operated phaser is provided by atiming wheel 130 integral to the annular plate 122, while timingfeedback from the electrically operated phaser is provided by a timingwheel 134 formed as a plate fitted to the front of the dual phaser. Thistiming wheel 134 is connected for rotation with the electricallyoperated phaser output via three projections 138 on the output gear 136of the electrically operated phaser that pass with clearance throughcutouts 144 in the front plate 112 of the hydraulically operated phaserand are engaged by three small fixing screws 142 to secure the timingwheel 134 in position.

A bias spring 150 mounted to the rear end plate 110 of the phaser (shownonly in FIG. 4) engages with the output plate 122 of the hydraulicallyoperated phaser to provide a bias torque on the hydraulically operatedphaser which can counteract the inherent drag-torque of the camshaft.

FIGS. 3 and 4 illustrate how the dual phaser assembly is mounted to aconcentric camshaft, generally designated 160, to provide independenttiming control of two sets of cam lobes.

A phaser mounting plate 132 is fitted to the camshaft front bearing 162via three fixing bolts 164, and this mounting plate provides threespigots 168, fitted with three bushes 169, for connection to the outputplate 122 of the hydraulically operated phaser, the entire dual phaserbeing secured in place by three screws 171. The drive connection betweenthe electrically operated phaser output gear 136 and the innerdriveshaft of the camshaft is achieved via a drive coupling 170, such asan Oldham coupling, that can transmit drive torque without imposing anyradial position constraint between the phaser and the inner shaft 172 ofthe camshaft 160, and a fixing bolt 140 to secure the axial position ofthe inner shaft to the electrically operated phaser output gear 136.

FIG. 4 shows the dual phaser assembled to the concentric camshaft 160and illustrates how oil feeds 173 to control the timing of thehydraulically operated phaser can be provided by the front bearing 162of the camshaft. The electric motor 180 for controlling the electricallyoperated phaser timing is also shown, mounted concentrically to thecamshaft 160 to a stationary part of the engine e.g. the front cover.The motor 180 engages with the electrically operated phaser via a drivecoupling 182 and serves to rotate gear set 120 epicyclically relative tothe input gear 118 and the output gear 136.

The internal gearset 120 has two gears that are fast in rotation withone another but have a different number of teeth. The first gear mesheswith the internal input gear 118, and the second gear meshes with theoutput gear 136. The gear ratio between the input gear 118 and the firstgear of the gearset 120 differs from the gear ratio between the secondgear of the gearset 120 and the output gear 136. The difference betweenthe two gear ratios causes the angular position of the output gear 136to change relative to the input gear 118.

To maintain the same phase between the input from the crankshaft and theinner camshaft 172, the motor 180 must rotate the gearset 120 at thesame speed as the input gear 118. If the motor 180 rotates at a speeddifferent to the input gear 118, the first gear of the eccentric gearset120 rotates and meshes at a different point within the input gear 118,causing rotation of the second gear and therefore the output gear 136.Once the desired phase is achieved, the motor 180 must again match therotational speed of the input gear 118 to maintain the desired phase.

FIG. 5 shows a section in a plane through the dual phaser of FIGS. 2 to4 and illustrates how the electrically operated phaser output gear 136is radially supported by the hydraulically operated phaser output plate122 but can rotate relative to it.

Description of the Second Embodiment

To avoid unnecessary repetition, components serving the same function inthe different embodiments to be described herein have been allocatedreference numerals with the same last two digits and will not bedescribed again. Components of the first embodiment have numerals in the100 series while those of the second, embodiments have numerals in the200 series.

The second embodiment adopts the alternative drive configuration shownin FIG. 6 in which one phaser acts on both sets of cam lobes. The enginecrankshaft in this embodiment is connected to the input of thehydraulically operated phaser, the output of which acts on a first setof cam lobes directly. The output of the hydraulically operated phaseradditionally provides the drive input of the electrically operatedphaser, the output of which acts on the second set of cam lobes. Thus,the hydraulic phaser acts on all the cam lobes whereas the electricserves only to vary the phase of the second set of cam lobes relative tothe phase of the first set of cam lobes.

In FIG. 7, a sprocket 211 that is driven by the engine crankshaft formspart of, or is mounted to, the annular plate 222 which partially definesthe arcuate cavities 224 of the hydraulically operated phaser and servesas the input member of the hydraulically operated phaser. The vanes 214,movable within the cavities 224, are secured to both the phaser mountingplate 232 and to the front plate 212 by three clamping screws 216. Thevanes 214, the mounting plate 232 and the front plate 212 thus serve asthe output of the hydraulically operated phaser, which changes the phaseof the first set of cam lobes relative to the crankshaft. As the frontplate 212 has the input gear 218 of the electrically operated phaserformed within it, the output from the hydraulically operated phaserserves additionally as the input of the electrically operated phaser.

The timing wheel for the first set of cam lobes (not shown in FIG. 7)may be formed with or, connected for rotation with, either the mountingplate 232 or the front plate 212.

To maintain the same relative phase between the first and second set ofcam lobes, the motor (not shown) must rotate at the same speed as thefront plate 212. If the phase of the first set of cam lobes is to bechanged relative to the phase of the second set of cam lobes, then themotor must compensate by adjusting its speed relative to the front plate212.

1. A hybrid dual phaser assembly for mounting to an engine camshaft toallow the timing of two sets of cam lobes to be phased independently ofone another relative to a crankshaft of the engine, wherein the phaserassembly comprises an electrically operated phaser having intermeshinggears for transmitting torque to the camshaft and a phase control inputdriven by an electric motor to be mounted coaxially with the camshaft,and a hydraulically operated phaser having vanes movable within arcuatecavities, characterized in that the cavities of the hydraulicallyoperated phaser are defined in part by an annular member that radiallysurrounds, and axially overlaps, a gear of the electrically operatedphaser, which gear is rotatable relative to the annular member and formsradially inner boundary walls of the cavities.
 2. A dual phaser assemblyas claimed in claim 1, wherein sensor wheels are mounted for rotationwith output members of the electrically operated phaser and thehydraulically operated phaser to generate timing signals for each of thetwo sets of cam lobes.
 3. A dual phaser assembly as claimed in claim or2, wherein a bias spring is provided to act upon the output member ofthe hydraulically operated phaser.
 4. A dual phaser assembly as claimedin claim 1, further comprising a phaser mounting plate for mounting on acamshaft previously installed in an engine, the mounting plate beingconnectable to one of the electrically operated phaser and thehydraulically operated phaser subsequent to being mounted on thecamshaft.
 5. A dual phaser assembly as claimed in claim 4, wherein asensor wheel is formed as part of, or directly mounted to, the phasermounting plate.
 6. A dual phaser assembly as claimed in claim 1, whereina drive connection between the electrically operated phaser output and arespective set of cam lobes comprises a drive coupling and a fixing boltthat passes through the drive coupling and acts to clamp the couplingaxially between the dual phaser and the camshaft.
 7. A camshaft assemblycomprising a dual phaser assembly as claimed in claim 1, mounted to aconcentric camshaft on which the two sets of cam lobes are mountedcoaxially.
 8. A camshaft assembly as claimed in claim 7, wherein each ofthe electrically operated phaser and the hydraulically operated phaserhas a respective input member to be driven in synchronism with theengine crankshaft and is operative to vary the phase of an output memberconnected to drive only a respective one of the two sets of cam lobes.9. A camshaft assembly as claimed in claim 7, wherein the hydraulicallyoperated phaser has an input member to be driven in synchronism with theengine crankshaft and an output member connected to drive an inputmember of the electrically operated phaser and one of the two sets ofcam lobes, an output member of the electrically operated phaser beingconnected to drive the second set of cam lobes in order to vary thephase of the two sets of cam lobes relative to one another.